Darin F. Ullman, an economist who recently received his PhD from the University of Wisconsin at Milwaukee, wanted to know what effect, if any, the enactment of medical marijuana laws has had on employee absentee rates.

A fair amount of research has been done on the aggregate impact of illicit marijuana use on workplace productivity. Generally speaking, the most recent research — gathered and summarized in this 2014 paper — indicates that most marijuana use has little effect on workplace productivity, although chronic or heavy pot use can be a problem.

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But there hasn’t been a lot of research into the impact of licit marijuana use — particularly medical marijuana use — on the workplace. So Ullman decided to look into what happened to employee sick-day use in states that legalized medical marijuana, according to the Bureau of Labor Statistics’ Current Population Survey (CPS).

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So Ullman examined before-and-after sick-day data from 24 states that had medical marijuana laws at the time of his study. On average, he found that “respondents were 8% less likely to report being absent from work due to health issues after medical marijuana laws” were passed. The CPS numbers also suggest that states with fewer restrictions on the use of medical marijuana, such as on the number of conditions it could be recommended for, had more of a decrease in sick-day use than states with stricter regulations.

It is important to note that this study does not prove a definitive link between medical marijuana laws and absenteeism, but it goes a long way to dispelling the idea that marijuana causes decreased productivity. As with most issues surrounding marijuana, more research is needed.